Hepatocyte activation and liver injury following cerebral ischemia promote HMGB1-mediated hepcidin upregulation in hepatocytes and regulation of systemic iron levels.

We previously reported that high mobility group box 1 (HMGB1), a danger-associated molecular pattern (DAMP), increases intracellular iron levels in the postischemic brain by upregulating hepcidin, a key regulator of iron homeostasis, triggering ferroptosis. Since hepatocytes are the primary cells that produce hepcidin and control systemic iron levels, we investigated whether cerebral ischemia induces hepcidin upregulation in hepatocytes. Following middle cerebral artery occlusion (MCAO) in a rodent model, significant liver injury was observed.

Taurine Chloramine-Mediated Nrf2 Activation and HO-1 Induction Confer Protective Effects in Astrocytes.

Taurine is ubiquitously distributed in mammalian tissues, with the highest levels in the brain, heart, and leukocytes. Taurine reacts with hypochlorous acid (HOCl) to produce taurine chloramine (Tau-Cl) via the myeloperoxidase (MPO) system. In this study, we elucidated the antioxidative and protective effects of Tau-Cl in astrocytes.

Age-Dependent and Aβ-Induced Dynamic Changes in the Subcellular Localization of HMGB1 in Neurons and Microglia in the Brains of an Animal Model of Alzheimer's Disease.

HMGB1 is a prototypical danger-associated molecular pattern (DAMP) molecule that co-localizes with amyloid beta (Aβ) in the brains of patients with Alzheimer's disease. HMGB1 levels are significantly higher in the cerebrospinal fluid of patients. However, the cellular and subcellular distribution of HMGB1 in relation to the pathology of Alzheimer's disease has not yet been studied in detail.

HMGB1 induces hepcidin upregulation in astrocytes and causes an acute iron surge and subsequent ferroptosis in the postischemic brain.

Dysregulation of brain iron levels causes functional disturbances and damages neurons. Hepcidin (a peptide hormone) plays a principal role in regulating intracellular iron levels by modulating ferroportin (FPN, the only known iron exporter) through triggering its internalization and lysosomal degradation. We observed a significant and rapid iron surge in the cortices of ischemic hemispheres at 3 h after cerebral ischemia (middle cerebral artery occlusion, MCAO) that was maintained until 4 d post-MCAO.

Cytosolic HMGB1 Mediates LPS-Induced Autophagy in Microglia by Interacting with NOD2 and Suppresses Its Proinflammatory Function.

The high mobility group box 1 (HMGB1), a well-known danger-associated molecule pattern (DAMP) molecule, is a non-histone chromosomal protein localized in the nucleus under normal physiological conditions. HMGB1 exhibits diverse functions depending on its subcellular location. In the present study, we investigated the role of HMGB1-induced autophagy in the lipopolysaccharide (LPS)-treated BV2 microglial cell line in mediating the transition between the inflammatory and autophagic function of the nucleotide-binding oligomerization domain-containing 2 (NOD2), a cytoplasmic pattern-recognition receptor.

Intranasal Delivery of RGD-Containing Osteopontin Heptamer Peptide Confers Neuroprotection in the Ischemic Brain and Augments Microglia M2 Polarization.

Osteopontin (OPN), a phosphorylated glycoprotein, is induced in response to tissue damage and inflammation in various organs, including the brain. In our previous studies, we reported the robust neuroprotective effects of the icosamer OPN peptide OPNpt20, containing arginine-glycine-aspartic acid (RGD) and serine-leucine-alanine-tyrosine (SLAY) motifs, in an animal model of transient focal ischemia and demonstrated that its anti-inflammatory, pro-angiogenic, and phagocytosis inducing functions are responsible for the neuroprotective effects. In the present study, we truncated OPNpt20 to 13 or 7 amino acid peptides containing RGD (R) and/or SLAY (S) motifs (OPNpt13RS, OPNpt7R, OPNpt7RS, and OPNpt7S), and their neuroprotective efficacy was examined in a rat middle cerebral artery occlusion (MCAO) model.

Taurine Protects against Postischemic Brain Injury via the Antioxidant Activity of Taurine Chloramine.

Taurine is ubiquitously distributed in mammalian tissues and is highly concentrated in the heart, brain, and leukocytes. Taurine exerts neuroprotective effects in various central nervous system diseases and can suppress infarct formation in stroke. Taurine reacts with myeloperoxidase (MPO)-derived hypochlorous acid (HOCl) to produce taurine chloramine (Tau-Cl).

Adenosine Triphosphate Accumulated Following Cerebral Ischemia Induces Neutrophil Extracellular Trap Formation.

In ischemic stroke, neutrophils infiltrate damaged brain tissue immediately following the ischemic insult and aggravate inflammation via various mechanisms which include neutrophil extracellular traps (NETs) formation. In the present study, we showed that adenosine triphosphate (ATP), a DAMP molecule, accumulates in the brain and induces NETosis in brain parenchyma and in circulating neutrophils (PMNs) isolated from a murine model of stroke induced by middle cerebral artery occlusion (MCAO). Expression of peptidylarginine deiminase-4 (PAD4), which induces citrullination of histones H3 (CitH3) and initiates NETosis, was significantly enhanced in brain parenchyma and blood PMNs following MCAO.

Ninjurin 1 dodecamer peptide containing the N-terminal adhesion motif (N-NAM) exerts proangiogenic effects in HUVECs and in the postischemic brain.

Nerve injury-induced protein 1 (Ninjurin 1, Ninj1) is a cell adhesion molecule responsible for cell-to-cell interactions between immune cells and endothelial cells. In our previous paper, we have shown that Ninj1 plays an important role in the infiltration of neutrophils in the postischemic brain and that the dodecamer peptide harboring the Ninj1 N-terminal adhesion motif (N-NAM, Pro-Asn) inhibits infiltration of neutrophils in the postischemic brain and confers robust neuroprotective and anti-inflammatory effects. In the present study, we examinedt the pro-angiogenic effect of N-NAM using human umbilical vein endothelial cells (HUVECs) and rat MCAO (middle cerebral artery occlusion) model of stroke.

Role of HMGB1 in the Interplay between NETosis and Thrombosis in Ischemic Stroke: A Review.

Neutrophil extracellular traps (NETs) comprise decondensed chromatin, histones and neutrophil granular proteins and are involved in the response to infectious as well as non-infectious diseases. The prothrombotic activity of NETs has been reported in various thrombus-related diseases; this activity can be attributed to the fact that the NETs serve as a scaffold for cells and numerous coagulation factors and stimulate fibrin deposition. A crosstalk between NETs and thrombosis has been indicated to play a role in numerous thrombosis-related conditions including stroke.

Osteopontin heptamer peptide containing the RGD motif enhances the phagocytic function of microglia.

Osteopontin (OPN) is a phosphorylated glycoprotein expressed in various tissues, including brain, and mediates a wide range of cellular activities. In our previous studies, we reported recombinant OPN and RGD and SLAY-containing OPN-peptide icosamer (OPNpt20) exhibited robust neuroprotective activities in an animal model of transient focal ischemia, and attributed these effects to the anti-inflammatory, pro-angiogenic, and phagocytic functions of OPNpt20. In the present study, we truncated OPNpt20 to 13 or 7 amino acid peptides containing RGD (R) and/or SLAY (S) motif (OPNpt13RS, OPNpt7R, OPNpt7RS, and OPNpt7S) and their cell motility and migration inducing activities were examined in BV2 cells (a microglia cell line).

Neutrophil extracellular trap induced by HMGB1 exacerbates damages in the ischemic brain.

It has been reported that neutrophil extracellular traps (NETs) play important roles in non-infectious diseases. In ischemic stroke, neutrophils infiltrate damaged brain tissue soon after injury and aggravate inflammation. Using a rat permanent MCAO model, we showed citrullinated histone H3 (CitH3, a marker of NETosis) induction in neutrophils in leptomeninges and in peripheral blood soon after MCAO.

Anti-Inflammatory and Neuroprotective Effects of DIPOPA (N,N-Diisopropyl-2-Oxopropanamide), an Ethyl Pyruvate Bioisoster, in the Postischemic Brain.

Ethyl pyruvate (EP) is a simple aliphatic ester of pyruvic acid and has been shown to have protective properties, which have been attributed to its anti-inflammatory, anti-oxidative, and anti-apoptotic functions. In an effort to develop better derivatives of EP, we previously synthesized DEOPA (N,N-diethyl-2-oxopropanamide, a novel isoster of EP) which has greater neuroprotective effects than EP, probably due to its anti-inflammatory and anti-excitotoxic effects. In the present study, we synthesized 3 DEOPA derivatives, in which its diethylamino group was substituted with diisopropylamino, dipropylamino, or diisobutylamino groups.

Gastrodin exerts robust neuroprotection in the postischemic brain via its protective effect against Zn-toxicity and its anti-oxidative effects in astrocytes.

Gastrodin (GAS) is a predominant bioactive constituent of the Chinese herbal medicine Tianma ( Blume). Many authors have reported GAS has the beneficial effect on diverse diseases of the CNS, including epilepsy, Alzheimer's disease, Parkinson's disease, and cerebral ischemia. Here, we report GAS exhibited a robust neuroprotective effect in an Sprague-Dawley rat model of stroke (transient middle cerebral artery occlusion, tMCAO), and show that the underlying molecular mechanism involves its protective effect against Zn-toxicity and its anti-oxidative effects in astrocytes.

Alarmin HMGB1 induces systemic and brain inflammatory exacerbation in post-stroke infection rat model.

Post-stroke infection (PSI) is known to worsen functional outcomes of stroke patients and accounts to one-third of stroke-related deaths in hospital. In our previous reports, we demonstrated that massive release of high-mobility group box protein 1 (HMGB1), an endogenous danger signal molecule, is promoted by N-methyl-D-aspartic acid-induced acute damage in the postischemic brain, exacerbating neuronal damage by triggering delayed inflammatory processes. Moreover, augmentation of proinflammatory function of lipopolysaccharides (LPS) by HMGB1 via direct interaction has been reported.

Proangiogenic functions of an RGD-SLAY-containing osteopontin icosamer peptide in HUVECs and in the postischemic brain.

Osteopontin (OPN) is a phosphorylated glycoprotein secreted into body fluids by various cell types. OPN contains arginine-glycine-aspartate (RGD) and serine-leucine-alanine-tyrosine (SLAY) motifs that bind to several integrins and mediate a wide range of cellular processes. In the present study, the proangiogenic effects of a 20-amino-acid OPN peptide (OPNpt20) containing RGD and SLAY motifs were examined in human umbilical vein endothelial cells (HUVECs) and in a rat focal cerebral ischemia model.

Osteopontin Peptide Icosamer Containing RGD and SLAYGLR Motifs Enhances the Motility and Phagocytic Activity of Microglia.

Osteopontin (OPN) is a secreted glycoprotein that is expressed in various tissues, including brain, and mediates a wide range of cellular activities. In a previous study, the authors observed the robust neuroprotective effects of recombinant OPN and of RGD and SLAYGLR-containing OPN-peptide icosamer (OPNpt20) in an animal model of transient focal ischemia, and demonstrated anti-inflammatory and pro-angiogenic effects of OPNpt20 in the postischemic brain. In the present study, we investigated the effects of OPNpt20 on the motility and phagocytic activity of BV2 cells (a microglia cell line).

Neuroprotective and Anti-inflammatory Effects of a Dodecamer Peptide Harboring Ninjurin 1 Cell Adhesion Motif in the Postischemic Brain.

It has been reported that the innate immune response plays important roles in brain ischemia and that the infiltration of blood-derived immune cells is a key initiator of this response. Nerve injury-induced protein 1 (Ninjurin 1, Ninj1) is a cell adhesion molecule responsible for cell-to-cell interactions between immune cells and endothelial cells. In the present study, we investigated the proinflammatory and neuroprotective effects of Ninj1 and a dodecamer peptide harboring Ninj1 N-terminal adhesion motif (N-NAM, Pro26~Asn37) in a rat middle cerebral artery occlusion (MCAO) model of stroke.

Anti-Zn-Toxicity of 4-Hydroxybenzyl Alcohol in Astrocytes and Neurons Contribute to a Robust Neuroprotective Effects in the Postischemic Brain.

4-Hydroxybenzyl alcohol (4-HBA) is an important phenolic constituent of Gastrodia elata (GE) Blume, which is used as a traditional herbal medicine in East Asia. Many activities have been reported to underlie the beneficial effects of 4-HBA in brain, such as, anti-oxidative, anti-inflammatory, anti-excitotoxic, and anti-apoptotic effects in neurons and microglia. Here, the authors demonstrate the robust neuroprotective effects of 4-HBA in rat middle cerebral artery occlusion (MCAO) model of stroke, and showed anti-Zn toxicity in neurons and astrocytes as a molecular mechanism contributing to these effects.

Anti-oxidative effects of 4-hydroxybenzyl alcohol in astrocytes confer protective effects in autocrine and paracrine manners.

4-Hydroxybenzyl alcohol (4-HBA) is an important phenolic constituent of Gastrodia elata Blume (GEB), a traditional herbal medicine used in East Asia. Many activities have been reported to underlie the beneficial effects of 4-HBA in the brain, and in particular, its anti-inflammatory, anti-oxidative, and anti-zinc-toxic effects have been implicated in the postischemic brain. Here, the authors investigated the anti-oxidative effect of 4-HBA on astrocytes and sought to identify the underlying molecular mechanisms involved.

Anti-inflammatory and anti-excitoxic effects of diethyl oxopropanamide, an ethyl pyruvate bioisoster, exert robust neuroprotective effects in the postischemic brain.

Ethyl pyruvate (EP) is a simple aliphatic ester of pyruvic acid and has been shown to have robust neuroprotective effects via its anti-inflammatory, anti-oxidative, and anti-apoptotic functions. In an effort to develop novel EP derivatives with greater protective potencies than EP, we generated four EP isosteres, among them the neuroprotective potency of N,N-diethyl-2-oxopropanamide (DEOPA), in which the ethoxy group of EP was replaced with diethylamine, was far greater than that of EP. When DEOPA was administered intravenously (5 mg/kg) to rat middle cerebral artery occlusion (MCAO) model at 6 hrs post-surgery, it suppressed infarct formation, ameliorated neurological and sensory/motor deficits, and inhibited microglial activation and neutrophil infiltrations in the postischemic brain more effectively than EP.

Neuroprotective effect of triflusal and its main metabolite, 2-hydroxy-4-trifluoromethylbenzoic acid (HTB), in the postischemic brain.

2-Hydroxy-4-trifluoromethylbenzoic acid (HTB) is a metabolite of triflusal (TF), and has been reported to exert anti-inflammatory effect. In this study, the authors investigated whether HTB has a neuroprotective effect against ischemic brain injuries. We showed that intravenous administration of HTB (5mg/kg) 30min before or 1, 3, or 6h after middle cerebral artery occlusion (MCAO) reduced brain infarct to 10.

Robust neuroprotective effects of 2-((2-oxopropanoyl)oxy)-4-(trifluoromethyl)benzoic acid (OPTBA), a HTB/pyruvate ester, in the postischemic rat brain.

Postischemic brain damage in stroke is proceded with complicated pathological events, and so multimodal drug treatments may offer better therapeutic means for improving clinical outcomes. Here, we report robust neuroprotective effects of a novel compound, 2-((2-oxopropanoyl)oxy)-4-(trifluoromethyl)benzoic acid (OPTBA), a 2-hydroxy-4-trifluoromethyl benzoic acid (HTB, a metabolite of triflusal)-pyruvate ester. Intravenous administration of OPTBA (5 mg/kg) 3 or 6 h after middle cerebral artery occlusion (MCAO) in Sprague-Dawley rats reduced infarct volumes to 38.

Enhanced cell survival of pH-sensitive bioenergetic nucleotide nanoparticles in energy/oxygen-depleted cells and their intranasal delivery for reduced brain infarction.

Unlabelled: Nucleotides (NTs) (e.g., adenosine triphosphate) are very important molecules in the body.

Induction of Nerve Injury-Induced Protein 1 (Ninjurin 1) in Myeloid Cells in Rat Brain after Transient Focal Cerebral Ischemia.

Nerve injury-induced protein-1 (Ninjurin-1, Ninj1) was initially identified as a novel adhesion molecule in rat sciatic nerve and to be up-regulated in neurons and Schwann cells of distal nerve segments after nerve transection or crush injury. Recently, Ninj1 was found to act as a modulator of cell migration, angiogenesis, and apoptosis. Accumulating evidence indicates that innate immune response plays beneficial and deleterious roles in brain ischemia, and the trans-endothelial migration of blood-derived immune cells is key initiator of this response.